Eggshells – literature


Eggshell – formation, structure and meaning

Egg shell is formed in the hen’s biomineralisation process. This process involves combining the hydrated calcium ions Ca2+ with the bicarbonate anhydrate HCO3 formed in the presence of carbonate anhydriosis.

2 CO2 + H2O  ß——à 2 HCO3

Ca2+ +  2 HCO3  ß——à  Ca(HCO3)2

The calcium carbonate precipitating from the liquid environment has a porous structure and contains a small amount of organic substances (about 5%) [1]. Among the organic substances are proteins (about 1%) [2] and significant amounts of fatty acids (2% – 4%) in the form of lipids and lipoproteins [3]. The basic dye of the shells is the pigment biliverdin [4].

The main task of the egg shell is to protect the developing embryo against harmful external factors. In addition, the porous shell structure allows gas exchange. Skorupka is the source of a number of cations, mainly calcium. As a natural inorganic material, additionally reinforced with organic scaffolding, it is relatively durable.

Sources of calcium carbonate origin

A common source of calcium ion are synthetic and fossil forms of calcium carbonate (aragonite and calcite). The very high content of Ca2+ ions, the low cost of production and the relative high bioavailability (ie the degree of absorption by the human or animal body) is decisive.

Much more than natural mineral biogenic calcium carbonate is valued more than natural minerals. Biogenic calcium carbonate comes from, among others from shells of marine crustaceans and external skeletons of marine animals (including non-precious varieties of white coral), or just from shells of chicken eggs [note. Małgorzata Wiewióra].

In the case of biogenic calcium carbonate, characteristics such as its porosity (facilitating absorption) are important, as well as the presence of trace amounts of other elements (eg strontium and fluorine), beneficial for the metabolism of living organisms. The origin of natural calcium carbonate is important.

Hazards can be caused by low amounts of heavy metals. The main threat may be the presence of lead, aluminum, cadmium or mercury [5] – this is why the material should be obtained from reliable sources and from chickens using fully balanced food [note. Wojciech Wiewióra].

Chemical composition of eggshells

On the basis of the studies by Schaafsma et al. [6], it is believed that eggshells after hatching contain similar contents of calcium ions as synthetic calcium carbonate. In the case of egg shells, there are more [health benefits – WW] strontium and selenium. The reduced amount of harmful heavy metals in the shells of chicken eggs such as vanadium, chromium, lead, aluminum and cadmium may be caused by the impaired its bioavailability in the mother’s body. Among the trace amounts of other elements, the presence of selenium, zinc, copper and strontium is essential [7], [8]. It is believed that strontium has an inhibitory effect on osteoclasts and stimulates the activity of osteoblasts (bone forming cells).

According to Kusumi et al. [9] porous calcium carbonate originating from chicken egg shells is much more easily dissolved (digested) than its synthetic varieties and can more effectively improve bone mineral density [10], [11], [12], [13]. In addition, the antibacterial activity of proteins present in the shells of chicken eggs was observed [14], [15]. Of course, the possibility of multiplying harmful bacteria in case of defective storage of the shells should be avoided.

The role of calcium carbonate in deacidification of soils

Traditional methods of soil deacidification are based on the use of ground limestone, i.e. a relatively hard and hard-to-absorb stone limestone to neutralize organic acids. In addition, fossil calcium carbonate is often contaminated with significant amounts of magnesium, iron and manganese salts.

Own research and discussion of results [18]

In order to confirm the structure of egg shells, a number of analyzes were performed using advanced instrumental methods. The tests carried out were aimed at confirming the chemical structure of chicken egg shells and simple methods of instrumental analysis.

In the first place, the presence of calcium ions in the examined shells was demonstrated by means of X-rays.

In addition, on the basis of infrared studies (IR spectra in KBr pellets in the range of 400 to 4000 cm-1), the presence of calcium carbonate was demonstrated. It can be noticed the stretching and deformation vibrations of a permanent form of crystalline calcium carbonate – calcite [16]. Similar IR spectra are observed in the case of white coral [17]. The wide band at approx. 3400 cm-1 comes from a small amount of moisture in the sample.

The spectra made in the form of KBr pellets are characterized by relatively low noise and well-formed peaks. The use of much less labor-consuming in terms of sample preparation for testing the internal rebound technique (ATR) allows to obtain significantly lower quality spectra. It should be noted, however, that such spectra also contain all relevant information allowing for the presence of calcium carbonate in the test shells. Similar results can be obtained by a technique complementary to IR spectroscopy, i.e. by means of Raman scattering [17]. In this case, the bands are much narrower and the spectrum is easier to analyze.

Evaluation of two egg shell samples for deacidification and its enrichment in selected elements [18]

Two samples of crusted egg shells (dried, sterilized and ground product) were provided:

  1. coarse (0.5-2 mm)
  2. fine-grained (less than 0.05 mm).

On the basis of literature and own research, it can be concluded that the formulations provided contain calcium carbonate (calcite as a more stable crystal form).

Due to the significant fragmentation and the possibility of preparing aqueous suspensions, it was found that such preparations in the form of a dry or aqueous suspension are perfect for de-acidification of the soil and its enrichment in a number of beneficial trace elements improving plant growth.

  1. Arias JL1, Fink DJ, Xiao SQ, Heuer AH, Caplan AI.. Biomineralization and eggshells: cell-mediated acellular compartments of mineralized extracellular matrix. Int Rev Cytol. 1993;145:217-50. Link
  2. Daengprok W1, Garnjanagoonchorn W, Naivikul O, Pornsinlpatip P, Issigonis K, Mine Y. Chicken eggshell matrix proteins enhance calcium transport in the human intestinal epithelial cells, Caco-2.. J Agric Food Chem. 2003 Sep 24;51(20):6056-61. Link
  3. Miksík I1, Charvátová J, Eckhardt A, Deyl Z. Insoluble eggshell matrix proteins–their peptide mapping and partial characterization by capillary electrophoresis and high-performance liquid chromatography. Electrophoresis. 2003 Mar;24(5):843-52. Link
  4. Zhao R1, Xu GY, Liu ZZ, Li JY, Yang N. A study on eggshell pigmentation: biliverdin in blue-shelled chickens. Poult Sci. 2006 Mar;85(3):546-9. Link
  5. Whiting SJ. Safety of some calcium supplements questioned. Nutr Rev. 1994 Mar;52(3):95-7. Link
  6. Schaafsma A1, Pakan I, Hofstede GJ, Muskiet FA, Van Der Veer E, De Vries PJ. Mineral, amino acid, and hormonal composition of chicken eggshell powder and the evaluation of its use in human nutrition. Poult Sci. 2000 Dec;79(12):1833-8. Link
  7. Nakano T1, Ikawa NI, Ozimek L. Chemical composition of chicken eggshell and shell membranes. Poult Sci. 2003 Mar;82(3):510-4. Link
  8. Seeman E1, Devogelaer JP, Lorenc R, Spector T, Brixen K, Balogh A, Stucki G, Reginster JY. Strontium ranelate reduces the risk of vertebral fractures in patients with osteopenia. J Bone Miner Res. 2008 Mar;23(3):433-8. Link
  9. Kusumi N., Nakamura M., Tando Y., Suda T., Kudo K., Eggshell calcium solubility in stomach, Japanese Journal of Nutritional Assessment, 1999, 16, 291.
  10. Naomi Omi, Ikuko Ezawa. Effect of Egg-Shell Ca on Preventing of Bone Loss after Ovariectomy. Journal of Home Economics of J … / Volume 49 (1998) Issue 3. Link
  11. Naomi Omi, Ikuko Ezawa. Te effect of several natural calcium sources of bone mineral density in ovariectomized rats. Abstrakt konferencji: 1st Annual Meeting of Japan Osteoporosis Society, Kurashiki; 1999; str. 64.
  12. Masaki H, Nakatsuka Y, Miki T, Takamoto K, Ohnishi T, Suguro N, Kunou M, Kawamura M, Nishizawa Y, Morii H. Inhibitory effects of eggshell calcium on bone resorption in elderly subjects – comparison with calcium carbonate. Osteoporosis (Jpn) 2000;8:245-7.
  13. Takuji Murata, Tomoko Kuno, Masatoshi Hozumi, Hiroshi Tamai, Masahiro Takagi, Tatsuya Kamiwaki, Yoshio Itoh. Inhibitory Effect of Calcium (Derived from Eggshell)-Supplemented Chocolate on Absorption of Fat in Human Males. Nippon Eiyo Shokuryo Gakkaishi / Volume 51 (1998) Issue 4. Link
  14. Mine Y1, Oberle C, Kassaify Z. Eggshell matrix proteins as defense mechanism of avian eggs. J Agric Food Chem. 2003 Jan 1;51(1):249-53. Link
  15. Poland AL1, Sheldon BW. Altering the thermal resistance of foodborne bacterial pathogens with an eggshell membrane waste by-product. J Food Prot. 2001 Apr;64(4):486-92. Link
  16. Yves Nysa, Joël Gautrona, Juan M. Garcia-Ruizb, Maxwell T. Hinckec. Avian eggshell mineralization: biochemical and functional characterization of matrix proteins. Comptes Rendus Palevol Volume 3, Issues 6–7, October 2004, Pages 549-562. Link
  17. Kupka, H. M. Lin, L. Stobiriski, Ch.-H. Chen, W.-J. Liou, R. Wrzalik, Z. Flisak, Experimental and theoretical studies on corals. I. Toward understanding the origin of color in precious red corals from Raman and IR spectroscopies and DFT calculations. J. Raman Spectrosc., 2010; 47: 651-658.
  18. Tobald Kupka. Wydział Chemii Uniwersytet Opolski. Opracowanie na temat zastosowania rozdrobnionych skorupek jaj kurzych, jako dodatku do neutralizacji i wzbogacania kwaśnych gleb w rolnictwie i uprawie roślin ozdobnych
  19. Miksík I1, Eckhardt A, Sedláková P, Mikulikova K., Proteins of insoluble matrix of avian (gallus gallus) eggshell, Connect Tissue Res. 2007;48(1):1-8. Link
  20. Łukasz Szeleszczuk. Zakład Chemii Fizycznej, Wydział Farmaceutyczny, Warszawski Uniwersytet Medyczny. Skorupa jaja kurzego – niedoceniane źródło wapnia
  21. Dariusz Maciej Pisklak, Łukasz Szeleszczuk, Iwona Wawer. Department of Physical Chemistry, Faculty of Pharmacy, Medical University of Warsaw. 1H and 13C Magic-Angle Spinning Nuclear Magnetic Resonance
  22. Rola i znaczenie związków mineralnych w żywieniu zwierząt, Lubuski Ośrodek Doradztwa Rolniczego w Kalsku. Link



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